1. Field of the Invention
This invention relates to hybrid vehicles and, more particularly, to driving methods and hybrid propulsion systems for vehicles.
2. Description of the Related Art
U.S. Pat. No. 3,979,913 discloses a system for increasing the efficiency of an internal combustion engine (I C E) by converting the waste energy to drive a turbine. Output power from the turbine is used to supplement the basic power of the engine.
U.S. Pat. No. 4,300,353 discloses a hybrid vehicle propulsion system which utilizes an I C E, an afterburner, and a steam engine in combination for improved efficiency and reduced emission of pollutants.
U.S. Pat. No. 5,191,766 discloses a hybrid engine which utilizes the heat from the exhaust gases of I C E to generate steam externally of the cylinders of the engine. The steam is used to power turbines to supplement the engine.
U.S. Pat. No. 5,327,987 discloses a hybrid-propulsion car system having one axle driven by I C E and another axis driven by an electric motor. The waste heat of I C E is recovered by the engine cooling fluid, and is then heat exchanged with an evaporative fluid in a closed circuit. The evaporative fluid is vaporized by the heat of the engine cooling fluid to power a turbine which in turn drives an electric generator.
In conventional hybrid propulsion systems discussed above, the internal combustion engines consume fuel in continuous fashion during various phases of engine operation. Various attempts have been made to further improve the fuel consumption and reduce emission of pollutants. However, none of these attempts have achieved both of these requirements. Since, further, the steam turbines combined with the I C Es have low efficiency, the waste energy can not be fully recovered. Thus, the engines become large in size and the hybrid propulsion systems become complicated in structure.